@KJLav
To answer your questions individually,
1. What you are seeing here is known as DSE or Dirty Screen Effect. It's symptomatic of many cheaper LED backlit LCD panel TVs whereby uneven backlighting can reveal the array of LED's behind the screen - these are the vertical lines you can see.
It's not uncommon in many LCD TV's but to varying degrees. Many people, when buying an expensive TV play the panel lottery (as it's known in AV circles) where they will keep returning a TV until they get a panel which is free of DSE. This can take a while and can be futile.
In the case of Sky Glass, there's not a lot you can do other than request a swap, which you should do sooner rather than later. You might, or might not get a better panel, that's the lottery you play with backlit LCD TVs.
Glass is a mass-produced TV so there are variances in quality. You're paying a lot of money for it but you should decide whether you think it's worth trying for a better replacement.
As you say, once you've seen it, you can't unsee it. It's part of the reason I moved to OLED from a backlit LCD - there is no DSE with OLED TV's due to every pixel being self-emitting - no backlight is necessary.
2. Flickering should not be happening. This again is down to poor backlighting and software decoding of the image, so it's the fault of the Glass TV and is nothing to do with streaming. You can try different picture modes and try changing the auto backlight setting to see if it improves but it really shouldn't be happening on any picture mode to be honest.
Basically, I'd recommend contacting Sky for further troubleshooting, but if you are not happy with the quality of the TV for the price you have paid you should insist on a replacement. If this doesn't improve matters you can always buy a different smart TV and switch to Sky Stream which gives the same Sky streaming experience as you get on Glass. There's an interesting article here which might be worth a read.
